You really need a Scott or Michel catalogue to identify stamps. In this case your stamp is the German Germania type. This would make it Scott #89 or possibly 89a. Since the scan appears more violet to me than magenta, it could be the 89a variety.
From what I can see, this appears to be a wartime printing of the 60 pf violet, watermarked, Germania stamp. Printing lines are thick, cancel date is (19)19, and color is somewhat reddish. So, it is most likely Michel 92 II a, or 92 II b (out of the 3 possible color ranges).
It's free, and has a very wide variety of stamps from around the world. It may not be as detailed as an official catalogue, but it does have pictures and prices (which should be taken with a grain of salt, as should prices in any catalogue)...